The chart below is a look at the 10-year U.S. Treasury yield over the past five years. The small back-up in interest rates since April 29 is highlighted on the far right.

Business Insider/Matthew Boesler, data from Bloomberg

The next chart is a zoomed-out look at the 30-year secular bond bull market. The little blip hasn't even shown up on that chart yet.

Business Insider/Matthew Boesler, data from Bloomberg

In April, PIMCO boosted its holdings of Treasuries to the highest levels in over a year, and Gross said in his May investment letter that Treasuries "are better than the alternative (cash) as long as central banks and dollar reserve countries (China, Japan) continue to participate."